The amino acid L-serine has been found to be useful in the food industry, the animal feed industry and pharmaceutical industry as well as in human medicine. It serves as a building block for the synthesis of other industrial valuable products like for example L-tryptophan from indole and L-serine.
It is known that L-serine can be produced by the fermentation of coryneform bacteria strands. Thus for example a strain of Corynebacterium glycinophilum is capable of forming L-serine from glycine and carbohydrates (Kubota K, Kageyama K, Shiro T and Okumura S (1971) Journal of General Applications in Microbiology, 17: 167-168; Kubota K, Kageyama K, Maeyashiki I, Yamada K and Okumura S (1972) Journal of General Applications in Microbiology 18: 365). The enzyme L-serine-hydroxy methyl transferase here participates in the conversion of glycine to L-serine. (Kubota K and Yokozeki K (1989) Journal of Fermentation and Bioengineering, 67(6):387-390. These corynebacterium glycinophilum strands have a defective serine dehydrataze which produces undirected mutagenesis (Kubota K (1985) Improved production of L-serine by mutants of Corynebacterium glycinophilum with less serine dehydratase activity: Agricultural Biological Chemistry, 49:7-12). This enzymatic activity is (Pyridoxal 5′-Phosphate) dependent and not molecularly characterized. (Kubota K., Yokozeki K, Ozaki H. (1989) Effects of L-serine dehydratase activity on L-serine production by Corynebacterium glycinophilum of an examination of the properties of the enzyme. Agric. Biol. Chem. 49:7-12. From U.S. Pat. No. 4,528,273 a method of producing L-serine from glycine is known in which the microorganism serine dehydratase is negative.
Furthermore, L-serine can be produced fermentatively from methanol and glycine with the aid of methylotropic bacteria like for example Hyphomicorbiium (Izumi Y, Yoshida T, Miyazaki S S, Mitsunaga T, Ohshiro T, Shiamo M, Miyata A and Tanabe T (1993) Applied Microbiology and Biotechnology, 39: 427-432). In both cases the amino acid glycine must be introduced as a precursor for the formation of the amino acid L-serine.
In addition, coryneform bacteria are known which can produce the L-serine directly from carbohydrates without further addition of precursors.
This is advantageous for industrial scale economical production of L-serine since the L-serine can be made directly from carbohydrates without the expensive addition of precursors, these strands which belong to the family Corynebacterium glutamicum for resistance of the L-serine analog serine hydroxamate and -chloroalamin and are obtained by undirected mutagenesis {Yoshida H and Nakamaya K (197) NIHON-Nogli-Kagakukaishi 48: 201-208}.
There are also brevibacterium flavum strains known which have because of undirected mutagenesis defects, in the breakdown of L-serine, an unused activity of the serA coded 3-phosphoglycerate dehydrogenase and an overexpression of serB and serC genes deriving from escherichia coli (EP0931833A2).